includes/cache/MessageCache.php

   1 <?php
   2 /**
   3  * Localisation messages cache.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23
  24 /**
  25  * MediaWiki message cache structure version.
  26  * Bump this whenever the message cache format has changed.
  27  */
  28 define( 'MSG_CACHE_VERSION', 1 );
  29
  30 /**
  31  * Memcached timeout when loading a key.
  32  * See MessageCache::load()
  33  */
  34 define( 'MSG_LOAD_TIMEOUT', 60 );
  35
  36 /**
  37  * Memcached timeout when locking a key for a writing operation.
  38  * See MessageCache::lock()
  39  */
  40 define( 'MSG_LOCK_TIMEOUT', 30 );
  41 /**
  42  * Number of times we will try to acquire a lock from Memcached.
  43  * This comes in addition to MSG_LOCK_TIMEOUT.
  44  */
  45 define( 'MSG_WAIT_TIMEOUT', 30 );
  46
  47 /**
  48  * Message cache
  49  * Performs various MediaWiki namespace-related functions
  50  * @ingroup Cache
  51  */
  52 class MessageCache {
  53         /**
  54          * Process local cache of loaded messages that are defined in
  55          * MediaWiki namespace. First array level is a language code,
  56          * second level is message key and the values are either message
  57          * content prefixed with space, or !NONEXISTENT for negative
  58          * caching.
  59          */
  60         protected $mCache;
  61
  62         /**
  63          * Should  mean that database cannot be used, but check
  64          * @var bool $mDisable
  65          */
  66         protected $mDisable;
  67
  68         /**
  69          * Lifetime for cache, used by object caching.
  70          * Set on construction, see __construct().
  71          */
  72         protected $mExpiry;
  73
  74         /**
  75          * Message cache has its own parser which it uses to transform
  76          * messages.
  77          */
  78         protected $mParserOptions, $mParser;
  79
  80         /**
  81          * Variable for tracking which variables are already loaded
  82          * @var array $mLoadedLanguages
  83          */
  84         protected $mLoadedLanguages = array();
  85
  86         /**
  87          * Singleton instance
  88          *
  89          * @var MessageCache $instance
  90          */
  91         private static $instance;
  92
  93         /**
  94          * @var bool $mInParser
  95          */
  96         protected $mInParser = false;
  97
  98         /**
  99          * Get the signleton instance of this class
 100          *
 101          * @since 1.18
 102          * @return MessageCache
 103          */
 104         public static function singleton() {
 105                 if ( is_null( self::$instance ) ) {
 106                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 107                         self::$instance = new self(
 108                                 wfGetMessageCacheStorage(),
 109                                 $wgUseDatabaseMessages,
 110                                 $wgMsgCacheExpiry
 111                         );
 112                 }
 113
 114                 return self::$instance;
 115         }
 116
 117         /**
 118          * Destroy the singleton instance
 119          *
 120          * @since 1.18
 121          */
 122         public static function destroyInstance() {
 123                 self::$instance = null;
 124         }
 125
 126         /**
 127          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 128          * @param bool $useDB
 129          * @param int $expiry Lifetime for cache. @see $mExpiry.
 130          */
 131         function __construct( $memCached, $useDB, $expiry ) {
 132                 if ( !$memCached ) {
 133                         $memCached = wfGetCache( CACHE_NONE );
 134                 }
 135
 136                 $this->mMemc = $memCached;
 137                 $this->mDisable = !$useDB;
 138                 $this->mExpiry = $expiry;
 139         }
 140
 141         /**
 142          * ParserOptions is lazy initialised.
 143          *
 144          * @return ParserOptions
 145          */
 146         function getParserOptions() {
 147                 if ( !$this->mParserOptions ) {
 148                         $this->mParserOptions = new ParserOptions;
 149                         $this->mParserOptions->setEditSection( false );
 150                 }
 151
 152                 return $this->mParserOptions;
 153         }
 154
 155         /**
 156          * Try to load the cache from a local file.
 157          *
 158          * @param string $hash The hash of contents, to check validity.
 159          * @param string $code Optional language code, see documenation of load().
 160          * @return array The cache array
 161          */
 162         function getLocalCache( $hash, $code ) {
 163                 global $wgCacheDirectory;
 164
 165                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 166
 167                 # Check file existence
 168                 wfSuppressWarnings();
 169                 $file = fopen( $filename, 'r' );
 170                 wfRestoreWarnings();
 171                 if ( !$file ) {
 172                         return false; // No cache file
 173                 }
 174
 175                 // Check to see if the file has the hash specified
 176                 $localHash = fread( $file, 32 );
 177                 if ( $hash === $localHash ) {
 178                         // All good, get the rest of it
 179                         $serialized = '';
 180                         while ( !feof( $file ) ) {
 181                                 $serialized .= fread( $file, 100000 );
 182                         }
 183                         fclose( $file );
 184
 185                         return unserialize( $serialized );
 186                 } else {
 187                         fclose( $file );
 188
 189                         return false; // Wrong hash
 190                 }
 191         }
 192
 193         /**
 194          * Save the cache to a local file.
 195          * @param string $serialized
 196          * @param string $hash
 197          * @param string $code
 198          */
 199         function saveToLocal( $serialized, $hash, $code ) {
 200                 global $wgCacheDirectory;
 201
 202                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 203                 wfMkdirParents( $wgCacheDirectory, null, __METHOD__ ); // might fail
 204
 205                 wfSuppressWarnings();
 206                 $file = fopen( $filename, 'w' );
 207                 wfRestoreWarnings();
 208
 209                 if ( !$file ) {
 210                         wfDebug( "Unable to open local cache file for writing\n" );
 211
 212                         return;
 213                 }
 214
 215                 fwrite( $file, $hash . $serialized );
 216                 fclose( $file );
 217                 wfSuppressWarnings();
 218                 chmod( $filename, 0666 );
 219                 wfRestoreWarnings();
 220         }
 221
 222         /**
 223          * Loads messages from caches or from database in this order:
 224          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 225          * (2) memcached
 226          * (3) from the database.
 227          *
 228          * When succesfully loading from (2) or (3), all higher level caches are
 229          * updated for the newest version.
 230          *
 231          * Nothing is loaded if member variable mDisable is true, either manually
 232          * set by calling code or if message loading fails (is this possible?).
 233          *
 234          * Returns true if cache is already populated or it was succesfully populated,
 235          * or false if populating empty cache fails. Also returns true if MessageCache
 236          * is disabled.
 237          *
 238          * @param bool|string $code Language to which load messages
 239          * @throws MWException
 240          * @return bool
 241          */
 242         function load( $code = false ) {
 243                 global $wgUseLocalMessageCache;
 244
 245                 if ( !is_string( $code ) ) {
 246                         # This isn't really nice, so at least make a note about it and try to
 247                         # fall back
 248                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 249                         $code = 'en';
 250                 }
 251
 252                 # Don't do double loading...
 253                 if ( isset( $this->mLoadedLanguages[$code] ) ) {
 254                         return true;
 255                 }
 256
 257                 # 8 lines of code just to say (once) that message cache is disabled
 258                 if ( $this->mDisable ) {
 259                         static $shownDisabled = false;
 260                         if ( !$shownDisabled ) {
 261                                 wfDebug( __METHOD__ . ": disabled\n" );
 262                                 $shownDisabled = true;
 263                         }
 264
 265                         return true;
 266                 }
 267
 268                 # Loading code starts
 269                 $success = false; # Keep track of success
 270                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 271                 $where = array(); # Debug info, delayed to avoid spamming debug log too much
 272                 $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 273
 274                 # Local cache
 275                 # Hash of the contents is stored in memcache, to detect if local cache goes
 276                 # out of date (e.g. due to replace() on some other server)
 277                 if ( $wgUseLocalMessageCache ) {
 278
 279                         $hash = $this->mMemc->get( wfMemcKey( 'messages', $code, 'hash' ) );
 280                         if ( $hash ) {
 281                                 $cache = $this->getLocalCache( $hash, $code );
 282                                 if ( !$cache ) {
 283                                         $where[] = 'local cache is empty or has the wrong hash';
 284                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 285                                         $where[] = 'local cache is expired';
 286                                         $staleCache = $cache;
 287                                 } else {
 288                                         $where[] = 'got from local cache';
 289                                         $success = true;
 290                                         $this->mCache[$code] = $cache;
 291                                 }
 292                         }
 293                 }
 294
 295                 if ( !$success ) {
 296                         # Try the global cache. If it is empty, try to acquire a lock. If
 297                         # the lock can't be acquired, wait for the other thread to finish
 298                         # and then try the global cache a second time.
 299                         for ( $failedAttempts = 0; $failedAttempts < 2; $failedAttempts++ ) {
 300                                 $cache = $this->mMemc->get( $cacheKey );
 301                                 if ( !$cache ) {
 302                                         $where[] = 'global cache is empty';
 303                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 304                                         $where[] = 'global cache is expired';
 305                                         $staleCache = $cache;
 306                                 } else {
 307                                         $where[] = 'got from global cache';
 308                                         $this->mCache[$code] = $cache;
 309                                         $this->saveToCaches( $cache, 'local-only', $code );
 310                                         $success = true;
 311                                 }
 312
 313
 314                                 if ( $success ) {
 315                                         # Done, no need to retry
 316                                         break;
 317                                 }
 318
 319                                 # We need to call loadFromDB. Limit the concurrency to a single
 320                                 # process. This prevents the site from going down when the cache
 321                                 # expires.
 322                                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 323                                 $acquired = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
 324                                 if ( $acquired ) {
 325                                         # Unlock the status key if there is an exception
 326                                         $that = $this;
 327                                         $statusUnlocker = new ScopedCallback( function () use ( $that, $statusKey ) {
 328                                                 $that->mMemc->delete( $statusKey );
 329                                         } );
 330
 331                                         # Now let's regenerate
 332                                         $where[] = 'loading from database';
 333
 334                                         # Lock the cache to prevent conflicting writes
 335                                         # If this lock fails, it doesn't really matter, it just means the
 336                                         # write is potentially non-atomic, e.g. the results of a replace()
 337                                         # may be discarded.
 338                                         if ( $this->lock( $cacheKey ) ) {
 339                                                 $mainUnlocker = new ScopedCallback( function () use ( $that, $cacheKey ) {
 340                                                         $that->unlock( $cacheKey );
 341                                                 } );
 342                                         } else {
 343                                                 $mainUnlocker = null;
 344                                                 $where[] = 'could not acquire main lock';
 345                                         }
 346
 347                                         $cache = $this->loadFromDB( $code );
 348                                         $this->mCache[$code] = $cache;
 349                                         $success = true;
 350                                         $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 351
 352                                         # Unlock
 353                                         ScopedCallback::consume( $mainUnlocker );
 354                                         ScopedCallback::consume( $statusUnlocker );
 355
 356                                         if ( !$saveSuccess ) {
 357                                                 # Cache save has failed.
 358                                                 # There are two main scenarios where this could be a problem:
 359                                                 #
 360                                                 #   - The cache is more than the maximum size (typically
 361                                                 #     1MB compressed).
 362                                                 #
 363                                                 #   - Memcached has no space remaining in the relevant slab
 364                                                 #     class. This is unlikely with recent versions of
 365                                                 #     memcached.
 366                                                 #
 367                                                 # Either way, if there is a local cache, nothing bad will
 368                                                 # happen. If there is no local cache, disabling the message
 369                                                 # cache for all requests avoids incurring a loadFromDB()
 370                                                 # overhead on every request, and thus saves the wiki from
 371                                                 # complete downtime under moderate traffic conditions.
 372                                                 if ( !$wgUseLocalMessageCache ) {
 373                                                         $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 374                                                         $where[] = 'could not save cache, disabled globally for 5 minutes';
 375                                                 } else {
 376                                                         $where[] = "could not save global cache";
 377                                                 }
 378                                         }
 379
 380                                         # Load from DB complete, no need to retry
 381                                         break;
 382                                 } elseif ( $staleCache ) {
 383                                         # Use the stale cache while some other thread constructs the new one
 384                                         $where[] = 'using stale cache';
 385                                         $this->mCache[$code] = $staleCache;
 386                                         $success = true;
 387                                         break;
 388                                 } elseif ( $failedAttempts > 0 ) {
 389                                         # Already retried once, still failed, so don't do another lock/unlock cycle
 390                                         # This case will typically be hit if memcached is down, or if
 391                                         # loadFromDB() takes longer than MSG_WAIT_TIMEOUT
 392                                         $where[] = "could not acquire status key.";
 393                                         break;
 394                                 } else {
 395                                         $status = $this->mMemc->get( $statusKey );
 396                                         if ( $status === 'error' ) {
 397                                                 # Disable cache
 398                                                 break;
 399                                         } else {
 400                                                 # Wait for the other thread to finish, then retry
 401                                                 $where[] = 'waited for other thread to complete';
 402                                                 $this->lock( $cacheKey );
 403                                                 $this->unlock( $cacheKey );
 404                                         }
 405                                 }
 406                         }
 407                 }
 408
 409                 if ( !$success ) {
 410                         $where[] = 'loading FAILED - cache is disabled';
 411                         $this->mDisable = true;
 412                         $this->mCache = false;
 413                         # This used to throw an exception, but that led to nasty side effects like
 414                         # the whole wiki being instantly down if the memcached server died
 415                 } else {
 416                         # All good, just record the success
 417                         $this->mLoadedLanguages[$code] = true;
 418                 }
 419                 $info = implode( ', ', $where );
 420                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 421
 422                 return $success;
 423         }
 424
 425         /**
 426          * Loads cacheable messages from the database. Messages bigger than
 427          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 428          * on-demand from the database later.
 429          *
 430          * @param string $code Language code.
 431          * @return array Loaded messages for storing in caches.
 432          */
 433         function loadFromDB( $code ) {
 434                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 435                 $dbr = wfGetDB( DB_SLAVE );
 436                 $cache = array();
 437
 438                 # Common conditions
 439                 $conds = array(
 440                         'page_is_redirect' => 0,
 441                         'page_namespace' => NS_MEDIAWIKI,
 442                 );
 443
 444                 $mostused = array();
 445                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 446                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 447                                 $this->load( $wgLanguageCode );
 448                         }
 449                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 450                         foreach ( $mostused as $key => $value ) {
 451                                 $mostused[$key] = "$value/$code";
 452                         }
 453                 }
 454
 455                 if ( count( $mostused ) ) {
 456                         $conds['page_title'] = $mostused;
 457                 } elseif ( $code !== $wgLanguageCode ) {
 458                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 459                 } else {
 460                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 461                         # other than language code.
 462                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 463                 }
 464
 465                 # Conditions to fetch oversized pages to ignore them
 466                 $bigConds = $conds;
 467                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 468
 469                 # Load titles for all oversized pages in the MediaWiki namespace
 470                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 471                 foreach ( $res as $row ) {
 472                         $cache[$row->page_title] = '!TOO BIG';
 473                 }
 474
 475                 # Conditions to load the remaining pages with their contents
 476                 $smallConds = $conds;
 477                 $smallConds[] = 'page_latest=rev_id';
 478                 $smallConds[] = 'rev_text_id=old_id';
 479                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 480
 481                 $res = $dbr->select(
 482                         array( 'page', 'revision', 'text' ),
 483                         array( 'page_title', 'old_text', 'old_flags' ),
 484                         $smallConds,
 485                         __METHOD__ . "($code)-small"
 486                 );
 487
 488                 foreach ( $res as $row ) {
 489                         $text = Revision::getRevisionText( $row );
 490                         if ( $text === false ) {
 491                                 // Failed to fetch data; possible ES errors?
 492                                 // Store a marker to fetch on-demand as a workaround...
 493                                 $entry = '!TOO BIG';
 494                                 wfDebugLog(
 495                                         'MessageCache',
 496                                         __METHOD__
 497                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 498                                 );
 499                         } else {
 500                                 $entry = ' ' . $text;
 501                         }
 502                         $cache[$row->page_title] = $entry;
 503                 }
 504
 505                 $cache['VERSION'] = MSG_CACHE_VERSION;
 506                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 507
 508                 return $cache;
 509         }
 510
 511         /**
 512          * Updates cache as necessary when message page is changed
 513          *
 514          * @param string $title Name of the page changed.
 515          * @param mixed $text New contents of the page.
 516          */
 517         public function replace( $title, $text ) {
 518                 global $wgMaxMsgCacheEntrySize;
 519
 520                 if ( $this->mDisable ) {
 521
 522                         return;
 523                 }
 524
 525                 list( $msg, $code ) = $this->figureMessage( $title );
 526
 527                 $cacheKey = wfMemcKey( 'messages', $code );
 528                 $this->load( $code );
 529                 $this->lock( $cacheKey );
 530
 531                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 532
 533                 if ( $text === false ) {
 534                         # Article was deleted
 535                         $this->mCache[$code][$title] = '!NONEXISTENT';
 536                         $this->mMemc->delete( $titleKey );
 537                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 538                         # Check for size
 539                         $this->mCache[$code][$title] = '!TOO BIG';
 540                         $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );
 541                 } else {
 542                         $this->mCache[$code][$title] = ' ' . $text;
 543                         $this->mMemc->delete( $titleKey );
 544                 }
 545
 546                 # Update caches
 547                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 548                 $this->unlock( $cacheKey );
 549
 550                 // Also delete cached sidebar... just in case it is affected
 551                 $codes = array( $code );
 552                 if ( $code === 'en' ) {
 553                         // Delete all sidebars, like for example on action=purge on the
 554                         // sidebar messages
 555                         $codes = array_keys( Language::fetchLanguageNames() );
 556                 }
 557
 558                 global $wgMemc;
 559                 foreach ( $codes as $code ) {
 560                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 561                         $wgMemc->delete( $sidebarKey );
 562                 }
 563
 564                 // Update the message in the message blob store
 565                 global $wgContLang;
 566                 MessageBlobStore::getInstance()->updateMessage( $wgContLang->lcfirst( $msg ) );
 567
 568                 Hooks::run( 'MessageCacheReplace', array( $title, $text ) );
 569
 570         }
 571
 572         /**
 573          * Is the given cache array expired due to time passing or a version change?
 574          *
 575          * @param array $cache
 576          * @return bool
 577          */
 578         protected function isCacheExpired( $cache ) {
 579                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 580                         return true;
 581                 }
 582                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 583                         return true;
 584                 }
 585                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 586                         return true;
 587                 }
 588
 589                 return false;
 590         }
 591
 592         /**
 593          * Shortcut to update caches.
 594          *
 595          * @param array $cache Cached messages with a version.
 596          * @param string $dest Either "local-only" to save to local caches only
 597          *   or "all" to save to all caches.
 598          * @param string|bool $code Language code (default: false)
 599          * @return bool
 600          */
 601         protected function saveToCaches( $cache, $dest, $code = false ) {
 602                 global $wgUseLocalMessageCache;
 603
 604                 $cacheKey = wfMemcKey( 'messages', $code );
 605
 606                 if ( $dest === 'all' ) {
 607                         $success = $this->mMemc->set( $cacheKey, $cache );
 608                 } else {
 609                         $success = true;
 610                 }
 611
 612                 # Save to local cache
 613                 if ( $wgUseLocalMessageCache ) {
 614                         $serialized = serialize( $cache );
 615                         $hash = md5( $serialized );
 616                         $this->mMemc->set( wfMemcKey( 'messages', $code, 'hash' ), $hash );
 617                         $this->saveToLocal( $serialized, $hash, $code );
 618                 }
 619
 620
 621                 return $success;
 622         }
 623
 624         /**
 625          * Represents a write lock on the messages key.
 626          *
 627          * Will retry MessageCache::MSG_WAIT_TIMEOUT times, each operations having
 628          * a timeout of MessageCache::MSG_LOCK_TIMEOUT.
 629          *
 630          * @param string $key
 631          * @return bool Success
 632          */
 633         function lock( $key ) {
 634                 $lockKey = $key . ':lock';
 635                 $acquired = false;
 636                 $testDone = false;
 637                 for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$acquired; $i++ ) {
 638                         $acquired = $this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT );
 639                         if ( $acquired ) {
 640                                 break;
 641                         }
 642
 643                         # Fail fast if memcached is totally down
 644                         if ( !$testDone ) {
 645                                 $testDone = true;
 646                                 if ( !$this->mMemc->set( wfMemcKey( 'test' ), 'test', 1 ) ) {
 647                                         break;
 648                                 }
 649                         }
 650                         sleep( 1 );
 651                 }
 652
 653                 return $acquired;
 654         }
 655
 656         function unlock( $key ) {
 657                 $lockKey = $key . ':lock';
 658                 $this->mMemc->delete( $lockKey );
 659         }
 660
 661         /**
 662          * Get a message from either the content language or the user language.
 663          *
 664          * First, assemble a list of languages to attempt getting the message from. This
 665          * chain begins with the requested language and its fallbacks and then continues with
 666          * the content language and its fallbacks. For each language in the chain, the following
 667          * process will occur (in this order):
 668          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 669          *     Note: for the content language, there is no /lang subpage.
 670          *  2. Fetch from the static CDB cache.
 671          *  3. If available, check the database for fallback language overrides.
 672          *
 673          * This process provides a number of guarantees. When changing this code, make sure all
 674          * of these guarantees are preserved.
 675          *  * If the requested language is *not* the content language, then the CDB cache for that
 676          *    specific language will take precedence over the root database page ([[MW:msg]]).
 677          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 678          *    the message is available *anywhere* in the language for which it is a fallback.
 679          *
 680          * @param string $key The message key
 681          * @param bool $useDB If true, look for the message in the DB, false
 682          *   to use only the compiled l10n cache.
 683          * @param bool|string|object $langcode Code of the language to get the message for.
 684          *   - If string and a valid code, will create a standard language object
 685          *   - If string but not a valid code, will create a basic language object
 686          *   - If boolean and false, create object from the current users language
 687          *   - If boolean and true, create object from the wikis content language
 688          *   - If language object, use it as given
 689          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 690          *
 691          * @throws MWException When given an invalid key
 692          * @return string|bool False if the message doesn't exist, otherwise the
 693          *   message (which can be empty)
 694          */
 695         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 696                 global $wgContLang;
 697
 698
 699                 if ( is_int( $key ) ) {
 700                         // Fix numerical strings that somehow become ints
 701                         // on their way here
 702                         $key = (string)$key;
 703                 } elseif ( !is_string( $key ) ) {
 704                         throw new MWException( 'Non-string key given' );
 705                 } elseif ( $key === '' ) {
 706                         // Shortcut: the empty key is always missing
 707                         return false;
 708                 }
 709
 710                 // For full keys, get the language code from the key
 711                 $pos = strrpos( $key, '/' );
 712                 if ( $isFullKey && $pos !== false ) {
 713                         $langcode = substr( $key, $pos + 1 );
 714                         $key = substr( $key, 0, $pos );
 715                 }
 716
 717                 // Normalise title-case input (with some inlining)
 718                 $lckey = strtr( $key, ' ', '_' );
 719                 if ( ord( $lckey ) < 128 ) {
 720                         $lckey[0] = strtolower( $lckey[0] );
 721                 } else {
 722                         $lckey = $wgContLang->lcfirst( $lckey );
 723                 }
 724
 725                 Hooks::run( 'MessageCache::get', array( &$lckey ) );
 726
 727                 if ( ord( $lckey ) < 128 ) {
 728                         $uckey = ucfirst( $lckey );
 729                 } else {
 730                         $uckey = $wgContLang->ucfirst( $lckey );
 731                 }
 732
 733                 // Loop through each language in the fallback list until we find something useful
 734                 $lang = wfGetLangObj( $langcode );
 735                 $message = $this->getMessageFromFallbackChain(
 736                         $lang,
 737                         $lckey,
 738                         $uckey,
 739                         !$this->mDisable && $useDB
 740                 );
 741
 742                 // If we still have no message, maybe the key was in fact a full key so try that
 743                 if ( $message === false ) {
 744                         $parts = explode( '/', $lckey );
 745                         // We may get calls for things that are http-urls from sidebar
 746                         // Let's not load nonexistent languages for those
 747                         // They usually have more than one slash.
 748                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 749                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 750                                 if ( $message === null ) {
 751                                         $message = false;
 752                                 }
 753                         }
 754                 }
 755
 756                 // Post-processing if the message exists
 757                 if ( $message !== false ) {
 758                         // Fix whitespace
 759                         $message = str_replace(
 760                                 array(
 761                                         # Fix for trailing whitespace, removed by textarea
 762                                         '&#32;',
 763                                         # Fix for NBSP, converted to space by firefox
 764                                         '&nbsp;',
 765                                         '&#160;',
 766                                 ),
 767                                 array(
 768                                         ' ',
 769                                         "\xc2\xa0",
 770                                         "\xc2\xa0"
 771                                 ),
 772                                 $message
 773                         );
 774                 }
 775
 776                 return $message;
 777         }
 778
 779         /**
 780          * Given a language, try and fetch a message from that language, then the
 781          * fallbacks of that language, then the site language, then the fallbacks for the
 782          * site language.
 783          *
 784          * @param Language $lang Requested language
 785          * @param string $lckey Lowercase key for the message
 786          * @param string $uckey Uppercase key for the message
 787          * @param bool $useDB Whether to use the database
 788          *
 789          * @see MessageCache::get
 790          * @return string|bool The message, or false if not found
 791          */
 792         protected function getMessageFromFallbackChain( $lang, $lckey, $uckey, $useDB ) {
 793                 global $wgLanguageCode, $wgContLang;
 794
 795                 $langcode = $lang->getCode();
 796                 $message = false;
 797
 798                 // First try the requested language.
 799                 if ( $useDB ) {
 800                         if ( $langcode === $wgLanguageCode ) {
 801                                 // Messages created in the content language will not have the /lang extension
 802                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 803                         } else {
 804                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 805                         }
 806                 }
 807
 808                 if ( $message !== false ) {
 809                         return $message;
 810                 }
 811
 812                 // Check the CDB cache
 813                 $message = $lang->getMessage( $lckey );
 814                 if ( $message !== null ) {
 815                         return $message;
 816                 }
 817
 818                 list( $fallbackChain, $siteFallbackChain ) =
 819                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 820
 821                 // Next try checking the database for all of the fallback languages of the requested language.
 822                 if ( $useDB ) {
 823                         foreach ( $fallbackChain as $code ) {
 824                                 if ( $code === $wgLanguageCode ) {
 825                                         // Messages created in the content language will not have the /lang extension
 826                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 827                                 } else {
 828                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 829                                 }
 830
 831                                 if ( $message !== false ) {
 832                                         // Found the message.
 833                                         return $message;
 834                                 }
 835                         }
 836                 }
 837
 838                 // Now try checking the site language.
 839                 if ( $useDB ) {
 840                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 841                         if ( $message !== false ) {
 842                                 return $message;
 843                         }
 844                 }
 845
 846                 $message = $wgContLang->getMessage( $lckey );
 847                 if ( $message !== null ) {
 848                         return $message;
 849                 }
 850
 851                 // Finally try the DB for the site language's fallbacks.
 852                 if ( $useDB ) {
 853                         foreach ( $siteFallbackChain as $code ) {
 854                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 855                                 if ( $message === false && $code === $wgLanguageCode ) {
 856                                         // Messages created in the content language will not have the /lang extension
 857                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 858                                 }
 859
 860                                 if ( $message !== false ) {
 861                                         // Found the message.
 862                                         return $message;
 863                                 }
 864                         }
 865                 }
 866
 867                 return false;
 868         }
 869
 870         /**
 871          * Get a message from the MediaWiki namespace, with caching. The key must
 872          * first be converted to two-part lang/msg form if necessary.
 873          *
 874          * Unlike self::get(), this function doesn't resolve fallback chains, and
 875          * some callers require this behavior. LanguageConverter::parseCachedTable()
 876          * and self::get() are some examples in core.
 877          *
 878          * @param string $title Message cache key with initial uppercase letter.
 879          * @param string $code Code denoting the language to try.
 880          * @return string|bool The message, or false if it does not exist or on error
 881          */
 882         function getMsgFromNamespace( $title, $code ) {
 883                 $this->load( $code );
 884                 if ( isset( $this->mCache[$code][$title] ) ) {
 885                         $entry = $this->mCache[$code][$title];
 886                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 887                                 // The message exists, so make sure a string
 888                                 // is returned.
 889                                 return (string)substr( $entry, 1 );
 890                         } elseif ( $entry === '!NONEXISTENT' ) {
 891                                 return false;
 892                         } elseif ( $entry === '!TOO BIG' ) {
 893                                 // Fall through and try invididual message cache below
 894                         }
 895                 } else {
 896                         // XXX: This is not cached in process cache, should it?
 897                         $message = false;
 898                         Hooks::run( 'MessagesPreLoad', array( $title, &$message ) );
 899                         if ( $message !== false ) {
 900                                 return $message;
 901                         }
 902
 903                         return false;
 904                 }
 905
 906                 # Try the individual message cache
 907                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 908                 $entry = $this->mMemc->get( $titleKey );
 909                 if ( $entry ) {
 910                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 911                                 $this->mCache[$code][$title] = $entry;
 912
 913                                 // The message exists, so make sure a string
 914                                 // is returned.
 915                                 return (string)substr( $entry, 1 );
 916                         } elseif ( $entry === '!NONEXISTENT' ) {
 917                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 918
 919                                 return false;
 920                         } else {
 921                                 # Corrupt/obsolete entry, delete it
 922                                 $this->mMemc->delete( $titleKey );
 923                         }
 924                 }
 925
 926                 # Try loading it from the database
 927                 $revision = Revision::newFromTitle(
 928                         Title::makeTitle( NS_MEDIAWIKI, $title ), false, Revision::READ_LATEST
 929                 );
 930                 if ( $revision ) {
 931                         $content = $revision->getContent();
 932                         if ( !$content ) {
 933                                 // A possibly temporary loading failure.
 934                                 wfDebugLog(
 935                                         'MessageCache',
 936                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 937                                 );
 938                                 $message = null; // no negative caching
 939                         } else {
 940                                 // XXX: Is this the right way to turn a Content object into a message?
 941                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 942                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 943                                 //       only used for wrapping them when needed.
 944                                 $message = $content->getWikitextForTransclusion();
 945
 946                                 if ( $message === false || $message === null ) {
 947                                         wfDebugLog(
 948                                                 'MessageCache',
 949                                                 __METHOD__ . ": message content doesn't provide wikitext "
 950                                                         . "(content model: " . $content->getContentHandler() . ")"
 951                                         );
 952
 953                                         $message = false; // negative caching
 954                                 } else {
 955                                         $this->mCache[$code][$title] = ' ' . $message;
 956                                         $this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
 957                                 }
 958                         }
 959                 } else {
 960                         $message = false; // negative caching
 961                 }
 962
 963                 if ( $message === false ) { // negative caching
 964                         $this->mCache[$code][$title] = '!NONEXISTENT';
 965                         $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 966                 }
 967
 968                 return $message;
 969         }
 970
 971         /**
 972          * @param string $message
 973          * @param bool $interface
 974          * @param string $language Language code
 975          * @param Title $title
 976          * @return string
 977          */
 978         function transform( $message, $interface = false, $language = null, $title = null ) {
 979                 // Avoid creating parser if nothing to transform
 980                 if ( strpos( $message, '{{' ) === false ) {
 981                         return $message;
 982                 }
 983
 984                 if ( $this->mInParser ) {
 985                         return $message;
 986                 }
 987
 988                 $parser = $this->getParser();
 989                 if ( $parser ) {
 990                         $popts = $this->getParserOptions();
 991                         $popts->setInterfaceMessage( $interface );
 992                         $popts->setTargetLanguage( $language );
 993
 994                         $userlang = $popts->setUserLang( $language );
 995                         $this->mInParser = true;
 996                         $message = $parser->transformMsg( $message, $popts, $title );
 997                         $this->mInParser = false;
 998                         $popts->setUserLang( $userlang );
 999                 }
1000
1001                 return $message;
1002         }
1003
1004         /**
1005          * @return Parser
1006          */
1007         function getParser() {
1008                 global $wgParser, $wgParserConf;
1009                 if ( !$this->mParser && isset( $wgParser ) ) {
1010                         # Do some initialisation so that we don't have to do it twice
1011                         $wgParser->firstCallInit();
1012                         # Clone it and store it
1013                         $class = $wgParserConf['class'];
1014                         if ( $class == 'ParserDiffTest' ) {
1015                                 # Uncloneable
1016                                 $this->mParser = new $class( $wgParserConf );
1017                         } else {
1018                                 $this->mParser = clone $wgParser;
1019                         }
1020                 }
1021
1022                 return $this->mParser;
1023         }
1024
1025         /**
1026          * @param string $text
1027          * @param Title $title
1028          * @param bool $linestart Whether or not this is at the start of a line
1029          * @param bool $interface Whether this is an interface message
1030          * @param string $language Language code
1031          * @return ParserOutput|string
1032          */
1033         public function parse( $text, $title = null, $linestart = true,
1034                 $interface = false, $language = null
1035         ) {
1036                 if ( $this->mInParser ) {
1037                         return htmlspecialchars( $text );
1038                 }
1039
1040                 $parser = $this->getParser();
1041                 $popts = $this->getParserOptions();
1042                 $popts->setInterfaceMessage( $interface );
1043                 $popts->setTargetLanguage( $language );
1044
1045                 if ( !$title || !$title instanceof Title ) {
1046                         global $wgTitle;
1047                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' . wfGetAllCallers( 5 ) . ' with no title set.' );
1048                         $title = $wgTitle;
1049                 }
1050                 // Sometimes $wgTitle isn't set either...
1051                 if ( !$title ) {
1052                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1053                         # Create a ghost title in such case
1054                         $title = Title::newFromText( 'Dwimmerlaik' );
1055                 }
1056
1057                 $this->mInParser = true;
1058                 $res = $parser->parse( $text, $title, $popts, $linestart );
1059                 $this->mInParser = false;
1060
1061
1062                 return $res;
1063         }
1064
1065         function disable() {
1066                 $this->mDisable = true;
1067         }
1068
1069         function enable() {
1070                 $this->mDisable = false;
1071         }
1072
1073         /**
1074          * Clear all stored messages. Mainly used after a mass rebuild.
1075          */
1076         function clear() {
1077                 $langs = Language::fetchLanguageNames( null, 'mw' );
1078                 foreach ( array_keys( $langs ) as $code ) {
1079                         # Global cache
1080                         $this->mMemc->delete( wfMemcKey( 'messages', $code ) );
1081                         # Invalidate all local caches
1082                         $this->mMemc->delete( wfMemcKey( 'messages', $code, 'hash' ) );
1083                 }
1084                 $this->mLoadedLanguages = array();
1085         }
1086
1087         /**
1088          * @param string $key
1089          * @return array
1090          */
1091         public function figureMessage( $key ) {
1092                 global $wgLanguageCode;
1093                 $pieces = explode( '/', $key );
1094                 if ( count( $pieces ) < 2 ) {
1095                         return array( $key, $wgLanguageCode );
1096                 }
1097
1098                 $lang = array_pop( $pieces );
1099                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1100                         return array( $key, $wgLanguageCode );
1101                 }
1102
1103                 $message = implode( '/', $pieces );
1104
1105                 return array( $message, $lang );
1106         }
1107
1108         /**
1109          * Get all message keys stored in the message cache for a given language.
1110          * If $code is the content language code, this will return all message keys
1111          * for which MediaWiki:msgkey exists. If $code is another language code, this
1112          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1113          * @param string $code Language code
1114          * @return array Array of message keys (strings)
1115          */
1116         public function getAllMessageKeys( $code ) {
1117                 global $wgContLang;
1118                 $this->load( $code );
1119                 if ( !isset( $this->mCache[$code] ) ) {
1120                         // Apparently load() failed
1121                         return null;
1122                 }
1123                 // Remove administrative keys
1124                 $cache = $this->mCache[$code];
1125                 unset( $cache['VERSION'] );
1126                 unset( $cache['EXPIRY'] );
1127                 // Remove any !NONEXISTENT keys
1128                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
1129
1130                 // Keys may appear with a capital first letter. lcfirst them.
1131                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
1132         }
1133 }